Heretofore, a system to be used in a semiconductor manufacturing process, provided with pipes for flowing various gases and others, requires a safety device for preventing gas leakage due to a malfunction of a pilot valve when the pipes are removed from the system for various operations or works. In a semiconductor manufacturing line, size reduction and cost reduction of each apparatus or device is always demanded. Accordingly, a combined valve integrally including a pilot valve and a manual valve serving as a safety device has been adopted up to now.
FIG. 13 is a sectional view of a conventional combined valve 101.
The conventional combined valve 101 includes a valve mechanism arranged to bring a diaphragm valve 103 into or out of contact with a valve seat 102. The combined valve 101 is integrally formed with a pilot valve and a manual valve, the pilot valve having a pilot mechanism for opening/closing a valve.
The pilot valve includes an operation port 104 connected to a not-shown supply/exhaust device via a joint 105. The pilot valve is configured to move pistons 110 and 111 upward and downward by a balance between a pressure of operation air supplied from the operation port 104 to piston chambers 107 and 108 via a supply/exhaust passage 106 and an elastic force of a restoring spring 109 to bring a diaphragm valve 103 into or out of contact with the valve seat 102.
A cylinder 113 of the pilot valve threadedly engages with a manual mechanism 114 of the manual valve. The manual mechanism 114 is configured by integrally coupling a handle 116, a manual stem 117, a sub handle 118, and a center rod 119 which are held in a housing 120 mounted on the cylinder 113. In the manual mechanism 114, a through hole 115 is formed in the sub handle 118 and the center rod 119, the through hole 115 being at a position corresponding to the operation port 104 and extending in a radial direction of the cylinder 113.
In the combined valve 101, when the manual mechanism 114 is rotated in a clockwise direction, the manual mechanism 114 is moved downward, bringing the diaphragm valve 103 into contact with the valve seat 102 through the piston rod 112. At this time, the through hole 115 is not communicated with the operation port 104 but is communicated with a not-shown exhaust port. Therefore, the valve is not opened even if the operation air is supplied to the operation port 104. When the manual mechanism 114 is rotated in a counter-clockwise direction, the manual mechanism 114 is moved upward to be separated from the piston rod 112, releasing a pressing force to press the diaphragm valve 103 to the valve seat 102. At this time, the operation port 104 is connected with the through hole 115 to communicate with the piston chambers 107 and 108 via the through hole 115. Thus, the pilot valve is enabled to freely conduct a valve opening/closing operation (see Patent Literature 1, for example).